1. Field of the Invention
The invention relates to a data recording apparatus, a data recording/reproducing apparatus, a data recording method, and a data recording/reproducing method which are applied to, for example, a case of recording image data onto a tape-shaped recording medium and reproducing the image data from the recording medium.
2. Description of the Related Art
A data recording/reproducing apparatus for recording a digital image signal onto a magnetic tape and reproducing a digital image signal from a recording medium is known as represented by a digital VTR (Video Tape Recorder). A shuffling process is performed in a recording processing unit in a digital image recording apparatus. The shuffling process is a process for setting a relation between a position of data on a screen and a recording position on the tape to a desired relation. It is the first object of the shuffling to distribute a burst error upon reproduction, thereby improving a correction ratio of the error correction by an error correction code such as a product code. The second object is to enable uncorrectable errors to be easily concealed. The third object is to enable a reproduction image to be easily seen upon high speed reproduction.
The shuffling process which is used in the conventional digital VTR will now be described. FIG. 1 shows a track pattern on which data of one frame of the digital VTR has been recorded. FIG. 1 shows a helical scan type VTR. Data of one frame is recorded as ten tracks T1 to T10 formed obliquely on the tape. Azimuths of the adjacent tracks are different.
Audio data is recorded in a center portion of each track and video data is recorded on the upper and lower sides of each track. The audio data and video data are subjected to the shuffling process and have been error correction encoded by a product code. The audio data and video data are recorded in a data format called a sync block. The sync block has a data structure in which a sync signal, a sync ID, data (audio data, a parity of an external code of the product code, or video data), and a parity of an internal code of the product code have been arranged in order from the head. For example, data of one macroblock is arranged in one sync block. The audio data and video data shown in FIG. 1 also include the parity of the external code and auxiliary data.
FIG. 2 shows a relation between the video data of one frame and the track on which the video data is recorded. In case of an NTSC television signal of 525 lines/60 fields, valid data of one frame is constructed by 45 macroblocks in the lateral direction and 32 macroblocks in the vertical direction. One macroblock is constructed by (16xc3x9716) pixels. The macroblock is a unit of a process in case of compressing the video data by MPEG2 (Moving Picture Experts Group Phase 2). The video data is encoded as variable length data by MPEG2. However, an amount of coded data of one frame is set to be constant by a length equalizing process. In case of compressing data by MPEG2, the coded data corresponding to one macroblock becomes the variable length data. Even in this case, at least significant data in the coded data of one macroblock is arranged into a data area of each sync block.
To record the video data of one frame into each of the upper and lower areas of 10 tracks, the video data of one frame is equally divided into five data in the lateral direction and equally divided into four data in the vertical direction, so that 20 recording units are formed. Each recording unit has a size of (9xc3x978=72 macroblocks). Among the 20 recording units, 10 recording units L1 to L10 of the upper half are video data that is recorded in the lower area of each track and 10 recording units U1 to U10 of the lower half are video data that is recorded in the upper area of each track. L1 and U1 are recording units which are recorded in the lower and upper areas of the track T1, respectively. Numerals which are added to the other recording units also correspond to the numbers of the tracks to be recorded.
As shown in FIG. 3, the shuffling process is performed every recording unit of (9xc3x978) macroblocks. That is, the recording unit is further divided into six subblocks of a size corresponding to (3xc3x974) macroblocks. In each subblock, as shown by an arrow in FIG. 3, three macroblocks arranged in the lateral direction are sequentially selected. When the selection of the macroblocks of one subblock is finished, the top three macroblocks of the second subblock adjacent to such a subblock are selected. When the selection of the macroblocks in the second subblock is finished and, further, the selection of the macroblocks in the third subblock is finished, the process advances to the lower leftmost subblock and the macroblocks in this subblock are selected. In this manner, the macroblocks selected in order shown by arrows in FIG. 3 are sequentially recorded in the area on the tape.
FIG. 4 shows an example of a construction for realizing the shuffling process. The input video data is written into an RAM (Random Access Memory) 161 and the data is read out of the RAM 161. The RAM 161 has a capacity of, for example, one frame and the video data is written into an address corresponding to the position in one frame of each macroblock. A read address in the RAM 161 is generated from a shuffling table 162. Although not shown, a write address in the RAM 161 is generated in accordance with the position of the macroblock on an image. An output of a counter 163 for generating a sync ID is supplied to the shuffling table 162. The position on the image of the macroblock and the recording position of the sync ID are converted into a predetermined relation by the shuffling table 162.
For example, the macro block numbers are specified as shown in FIG. 5A and the sync ID is specified as shown in FIG. 5B. FIGS. 5A and 5B show one recording unit which is recorded on the lower or upper area of one track. The data of each macroblock is recorded in the area on the tape in the scanning direction of the head in order of the numbers of the sync IDs. Although only the sync IDs will be described for simplicity of explanation, in order to record data onto the tape in the format shown in FIG. 1, track IDs to distinguish 10 tracks and an ID to distinguish the upper or lower area of each track are also necessary. The macroblock numbers and the values of the sync IDs are also set to simple numbers starting from 1 for simplicity of explanation. Actually, IDs to distinguish all sync blocks in one track or in the upper area or lower area in one track are used while including a parity of an external code, auxiliary data, and the like.
In case of the digital VTR, besides a normal reproducing operation in which a tape speed upon reproduction is equalized to that upon recording, a high speed reproducing operation in which the tape speed upon reproduction is higher than that upon recording can be performed. In the high speed reproducing mode, as the tape speed rises, a relative speed between the head and the tape changes and a trace locus which is formed when the head passes on the tape is deviated from the track. Thus, although the number of tracks over which the head passes increases, the number of sync blocks which are continuously reproduced from each track decreases and the macroblocks of a plurality of frames mixedly exist on an image and are updated. The position of the macroblock which is updated at each time in the high speed reproducing mode changes depending on a difference of shuffling tables (also called shuffling patterns) in which the position of the macroblock on the image and the recording position on the tape are made to correspond. Since only a part of information recorded on the tape can be obtained in the high speed reproducing mode, in order to enable a reproduction image in the high speed reproducing mode to be easily seen, it is necessary to design the shuffling table so that information can be obtained as much as possible.
FIG. 6 shows a relation between the track pattern in the high speed reproducing mode and the trace locus of the head. FIG. 6 shows the trace locus at each of the 2-times speed (xc3x972), 4-times speed (xc3x974), 7-times speed (xc3x977), 10-times speed (xc3x9710), 19-times speed (xc3x9719), and 37-times speed (xc3x9737) in the forward direction. A forward direction N-times speed mode corresponds to the reproducing operation in which the tape feeding direction is set to be identical to that upon recording and the tape speed is increased by N times. In each trace locus, reproduction data is obtained when the head is located on the track in which the azimuth coincides. When a rotary head traces the tape once, the reproduction data is obtained in a hatched portion in FIG. 6.
In the forward direction high speed reproducing mode, the reproduction data is obtained at the hatched position in one frame in FIGS. 7A to 7E. FIGS. 7A to 7E enlargedly show the obtained reproduction data on a recording unit basis. FIG. 7A shows the video data obtained in the 2-times speed reproducing mode. As will be understood from the trace locus in the 2-times speed reproducing mode shown in FIG. 6, the recording unit L1 in the lower area of the track T1 and the recording unit U1 in the upper area of the track T1 are reproduced by the trace of one time by the head. All data of the recording units L1 and U1 are obtained.
FIG. 7B shows the video data obtained in the 4-times speed reproducing mode. As will be understood from the trace locus in the 4-times speed reproducing mode shown in FIG. 6, the recording unit L1 in the lower area of the track T1 and the recording unit U3 in the upper area of the track T3 are reproduced by the trace of one time by the head. All data of the recording units L1 and U3 are obtained.
FIG. 7C shows the video data obtained in the 7-times speed reproducing mode. As will be understood from the trace locus in the 7-times speed reproducing mode, the data of the half of the recording unit L1 in the lower area of the track T1 and the data of the half of the recording unit U5 in the upper area of the track T5 are obtained by the trace of one time by the head.
Further, FIG. 7D shows the video data obtained in the 19-times speed reproducing mode and FIG. 7E shows the video data obtained in the 37-times speed reproducing mode. In the 19-times speed reproducing mode and the 37-times speed reproducing mode, since the tape speed is fairly high, an amount of data which is obtained in each recording unit decreases. However, the reproduced macroblocks included in the continuous sync IDs are coupled so as to form a rectangle in each recording unit. As mentioned above, in the foregoing conventional shuffling process, in the high speed reproducing mode, the macroblocks of a plurality of sync blocks which are continuously reproduced are coupled so as to form a rectangle on the image.
As another shuffling process, there is such a process that the positions on the screen of the video data obtained from the sync blocks which are continuously reproduced in the high speed reproducing mode are arranged at random. According to this process, the video data which could not be reproduced is interpolated by the video data which could be reproduced. Owing to this method, when a size of video data which is not compressed or a size of macroblock is small, since there is a correlation among the images of the approximate video data or macroblocks, the macroblocks which were not updated can be interpolated by the neighboring updated macroblocks. However, in case of compressing the video data by the size of relatively large macroblock such as a macroblock of (16xc3x9716) and recording it, since the interpolation by the adjacent macroblocks is not valid, the shuffling process in which the reproduced macroblocks are coupled so as to form a rectangular area as mentioned above is preferable.
As will be understood from FIG. 3, according to the conventional shuffling process, a plurality of macroblocks are not coupled in a rectangle when the data of a plurality of macroblocks is reproduced so as to exist over boundaries of the subblocks in the recording unit. As mentioned above, according to the conventional shuffling process, the reproduced macroblocks are not coupled so as to form a rectangle in all of the cases. Therefore, such a situation that the macroblocks are not coupled on the image although the sync ID are continuous occurs in dependence on the tape speed in the high speed reproducing mode. This problem is not limited to the tape speed but a similar problem occurs even in the case where a recording format (the number of tracks of one frame, a size of recording unit, or the like) is changed. That is, the shuffling pattern has to be determined in consideration of the recording frame or the tape speed in the high speed reproducing mode. There is such a problem that a high speed reproduction image having high visibility is not derived if the tape is reproduced at an unexpected tape speed or the recording format is different.
It is an object of the invention to provide a data recording apparatus, a data recording/reproducing apparatus, a data recording method, and a data recording/reproducing method which can perform such a shuffling process that a plurality of macroblocks which were continuously reproduced in the high speed reproducing mode are coupled in a rectangle without being influenced by a tape speed or a recording format.
According to a preferred aspect of the invention, there is provided a data recording apparatus in which a relation between a position on a display image of image data constructing the display image and a position on a tape-shaped recording medium of the image data in case of recording the image data subjected to a predetermined process onto the tape-shaped recording medium by rotary heads is converted and the image data whose positional relation has been converted is recorded onto the tape-shaped recording medium, comprising:
image block forming means for dividing the image data on a unit basis of a predetermined number and forming a plurality of image blocks;
sync block forming means for forming a sync block as a unit of recording the image blocks onto the tape-shaped recording medium from the image blocks;
shuffling means for performing the conversion from the position on the display image of the image blocks to the position on the tape-shaped recording medium of the sync blocks every recording unit constructed by a predetermined number of the image blocks, performing the conversion in such a manner that in a whole range of the recording unit, the plurality of image blocks included in the plurality of sync blocks which are continuous on the tape-shaped recording medium form an almost rectangle and are coupled, and performing the conversion in such a manner that when curves are drawn in accordance with the order of recording positions of the sync blocks in the recording unit, the curve is drawn so as to pass through all of the image blocks in the recording unit only once; and
recording means including a recording rotary head and for recording the sync block whose position has been converted by the shuffling means onto an inclined track of the tape-shaped recording medium.
According to another aspect of the invention, there is provided a data recording/reproducing apparatus in which a relation between a position on a display image of image data constructing the display image and a position on a tape-shaped recording medium of the image data in case of recording the image data subjected to a predetermined process onto the tape-shaped recording medium by rotary heads is converted, the image data whose positional relation has been converted is recorded onto the tape-shaped recording medium, and the image data in which the positional relation has been converted is reproduced from the tape-shaped recording medium, comprising:
image block forming means for dividing the image data on a unit basis of a predetermined number and forming a plurality of image blocks;
sync block forming means for forming a sync block as a unit of recording the image blocks onto the tape-shaped recording medium from the image blocks;
shuffling means for performing the conversion from the position on the display image of the image blocks to the position on the tape-shaped recording medium of the sync blocks every recording unit constructed by a predetermined number of the image blocks, performing the conversion in such a manner that in a whole range of the recording unit, the plurality of image blocks included in the plurality of sync blocks which are continuous on the tape-shaped recording medium form an almost rectangle and are coupled, and performing the conversion in such a manner that when curves are drawn in accordance with the order of recording positions of the sync blocks in the recording unit, the curve is drawn so as to pass through all of the image blocks in the recording unit only once;
recording means including a recording rotary head and for recording the sync block whose position has been converted by the shuffling means onto an inclined track of the tape-shaped recording medium;
reproducing means including a reproducing rotary head and for reproducing the sync block from the tape-shaped recording medium on which the position converted sync block has been recorded;
deshuffling means for performing a conversion opposite to the position conversion which is performed by the shuffling means to the sync block reproduced by the reproducing means, thereby forming the image blocks; and
image data forming means for reproducing the image data from the image blocks formed by the deshuffling means.
According to still another aspect of the invention, there is provided a data recording method whereby a relation between a position on a display image of image data constructing the display image and a position on a tape-shaped recording medium of the image data in case of recording the image data subjected to a predetermined process onto the tape-shaped recording medium by rotary heads is converted and the image data whose positional relation has been converted is recorded onto the tape-shaped recording medium, comprising:
an image block forming step of dividing the image data on a unit basis of a predetermined number and forming a plurality of image blocks;
a sync block forming step of forming a sync block as a unit of recording the image blocks onto the tape-shaped recording medium from the image blocks;
a shuffling step of performing the conversion from the position on said display image of the image blocks to the position on the tape-shaped recording medium of the sync blocks every recording unit constructed by a predetermined number of the image blocks, performing the conversion in such a manner that in a whole range of the recording unit, the plurality of image blocks included in the plurality of sync blocks which are continuous on the tape-shaped recording medium form an almost rectangle and are coupled, and performing the conversion in such a manner that when curves are drawn in accordance with the order of recording positions of the sync blocks in the recording unit, the curve is drawn so as to pass through all of the image blocks in the recording unit only once; and
a recording step of including a recording rotary head and recording the sync block whose position has been converted in the shuffling step onto an inclined track of the tape-shaped recording medium,
according to further another aspect of the invention, there is provided a data recording/reproducing method whereby a relation between a position on a display image of image data constructing the display image and a position on a tape-shaped recording medium of the image data in case of recording the image data subjected to a predetermined process onto the tape-shaped recording medium by rotary heads is converted, the image data whose positional relation has been converted is recorded onto the tape-shaped recording medium, and the image data in which the positional relation has been converted is reproduced from the tape-shaped recording medium, comprising:
an image block forming step of dividing the image data on a unit basis of a predetermined number and forming a plurality of image blocks;
a sync block forming step of forming a sync block as a unit of recording the image blocks onto the tape-shaped recording medium from the image blocks;
a shuffling step of performing the conversion from the position on the display image of the image blocks to the position on the tape-shaped recording medium of the sync blocks every recording unit constructed by a predetermined number of the image blocks, performing the conversion in such a manner that in a whole range of the recording unit, the plurality of image blocks included in the plurality of sync blocks which are continuous on the tape-shaped recording medium form an almost rectangle and are coupled, and performing the conversion in such a manner that when curves are drawn in accordance with the order of recording positions of the sync blocks in the recording unit, the curve is drawn so as to pass through all of the image blocks in the recording unit only once;
a recording step of including a recording rotary head and recording the sync block whose position has been converted in the shuffling step onto an inclined track of the tape-shaped recording medium;
a reproducing step of including a reproducing rotary head and for reproducing the sync block from the tape-shaped recording medium on which the position converted sync block has been recorded;
a deshuffling step of performing a conversion opposite to the position conversion which is performed in the shuffling step to the sync block reproduced in the reproducing step, thereby forming the image blocks; and
an image data forming step of reproducing the image data from the image blocks formed in the deshuffling step.
The above and other objects and features of the present invention will become apparent from the following detailed description and the appended claims with reference to the accompanying drawings.